Plants are adequately protected by the presence of multiple protein components in different organelles such as chloroplast, cytoplasm, mitochondria and peroxisomes. Therefore, investigation of organellar-specific proteome is important to understand the mechanism of function of protein subset in which they exert their particular function (Dreger, 2003).
In plants, cell wall or extra-cellular matrix (ECM) serves as the repository for most of the components of cell signaling process. In legumes, the majority of iron is represented by ferritin (Ambe et al., 1987; Burton et al., 1998) and used for nitrogen fixation by, nodules. Accumulation of nodule ferritin is developmentally regulated. Iron is recovered by nodule ferritin during nodule senescence and recycled by a mechanism yet to be identified. Classically, iron storage protein, ferritin, is reported to be present in the plastids. However, there are reports of ferritins being localized to other cellular compartments such as mitochondria and nucleus (Harrison and Arosio, 1996; Kwok and Richardson, 2004).
With completion of genome sequencing exercises and development of analytical methods for protein characterization, proteomics has become a major tool of functional genomics. This technology allows the global analyses of gene products in cells, organelles, and physiological state of cells. However, the application of proteomic approach at whole cell level is limited by several factors such as protein abundance, size, hydrophobicity, and other electrophoretic properties. The compartment specific proteome is thus important because fractionated subsets of proteins provide the suitable information in which they exert their particular function.